The success of the total hip replacement in recent years has prompted considerable interest in the development of total joint replacement for several other anatomical joints. The success of the total joint replacements is largely due to the materials being used; polymethylmethacrylate ("bone cement"), high density polyethylene and a suitable corrosion resistant metal. With the knee, however, several problems have been encountered. These problems, caused primarily by the severe loading conditions within the knee joint, have led to many different prosthesis designs, none of which appear to be entirely satisfactory.
There are basically two types of knee prostheses: The earlier hinge or pin type, illustrated, for example by U.S. Pat. No. 3,696,446 issued to Bousquet, et al, and the more recent condylar replacement type, illustrated by U.S. Pat. No. 3,816,855 issued to Saleh. The lack of rotation about the axis of the tibia in the hinge prosthesis may result in loosening of one of the components. This combined with pin wear and the excessive bone removal required has resulted in limited use of the hinge type prosthesis.
Among the more severe porblems with condylar replacement prostheses of the Saleh type are loosening of the tibial components at the bone-cement interface and bone resorption, and plastic deformation ("plastic flow") of the high density polyethylene due to the high stresses and dislocation of the joint. In addition, it is not understood what effect the functional behavior of the prosthesis itself has on the overall performance of the patient with the implanted device. Nearly all of the condylar replacement prosthesis designs have a metal femoral component shaped similar to the anatomical condyles and a polyethylene tibial component either flat or grooved to provide a track for the femoral "condyle."